Phenolic compounds constitute a large and diverse group of secondary metabolites derived from phenylalanine and tyrosine and are widely distributed throughout the plant kingdom. They could be divided into different classes such as simple phenol, phenyl acetic acid, hydroxybenzoic acid, hydroxycinnamic acid, and other phenylpropanoids as well as condensed tannins (proanthocyanidins) and hydrolysable tannins, among others, depending on their basic carbon skeleton structure. Phenolic compounds in plant-based foods have been suggested to have a number of beneficial health effects including prevention of cancer, cardiovascular disease, diabetes, immune disorders, neurogenerative disease and others. These properties are largely attributable to the antioxidant activity of the phenolic compounds as well as other mechanisms of action. Therefore, nutraceuticals of plant origin may evolve to be considered a vital aspect of dietary-disease preventive food components. Agri-food industries generate substantial quantities of phenolic rich by-products, which could serve as an attractive and commercially viable source of nutraceuticals. This contribution mainly summarizes the occurrence of phenolic compounds and some other bioactives in various Agri-food by-products, their bioavailability and health benefits.

The world fisheries resources have exceeded 160 million tons in recent years. However, every year a considerable amount of total catch is discarded as by-catch or as processing leftovers, and that includes trimmings, fins, frames, heads, skin, viscera and among others. In addition, a large quantity of processing by-products is accumulated as shells of crustaceans and shellfish from marine bioprocessing plants. Recognition of the limited marine resources and the increasing environmental pollution has emphasized the need for better utilization of the by-products. Marine by-products contain valuable protein and lipid fractions, minerals, enzymes as well as many other components. The major fraction of by-products are used for feed production—in making fish meal/oil, but this has low profitability. However, there are many ways in which the fish and shellfish waste could be better utilized, including the production of novel food ingredients, nutraceuticals, pharmaceuticals, biomedical materials, fine chemicals, and other value-added products. In recent times, much research is conducted in order to explore the possible uses of different by-products. This contribution primarily covers the characteristics and utilization of the main ingredients such as protein, lipid, chitin and its derivatives, enzymes, carotenoids, and minerals originating from marine by-products.

The world fisheries resources have exceeded 160 million tons in recent years. However, every year a considerable amount of total catch is discarded as by-catch or as processing leftovers, and that includes trimmings, fins, frames, heads, skin, viscera and among others. In addition, a large quantity of processing by-products is accumulated as shells of crustaceans and shellfish from marine bioprocessing plants. Recognition of the limited marine resources and the increasing environmental pollution has emphasized the need for better utilization of the by-products. Marine by-products contain valuable protein and lipid fractions, minerals, enzymes as well as many other components. The major fraction of by-products are used for feed production-in making fish meal/oil, but this has low profitability. However, there are many ways in which the fish and shellfish waste could be better utilized, including the production of novel food ingredients, nutraceuticals, pharmaceuticals, biomedical materials, fine chemicals, and other value-added products. In recent times, much research is conducted in order to explore the possible uses of different by-products. This contribution primarily covers the characteristics and utilization of the main ingredients such as protein, lipid, chitin and its derivatives, enzymes, carotenoids, and minerals originating from marine by-products.